Contamination of agricultural soils due to
human activities is a major concern globally. The use of
urban untreated wastewater for irrigation has been on-going
for a long time and the major driving forces of this
practice include water scarcity, easy availability, low/no
cost and wastewater as a source of plant nutrients. Contamination
of agricultural soils with heavy metals as a
result of using untreated wastewater for irrigation as well
as translocation of the heavy metal into the lettuce was
investigated. Soil samples were analysed for pH, electrical
conductivity, organic carbon, cation exchange capacity and
extractable heavy metals while lettuce samples were
analysed for total heavy metal content. The soil samples
were found to be sandy clay loam and sandy loamy in
texture and alkaline. The organic carbon contents were
found to be relatively low with low salt accumulations at
both farms. The heavy metal levels in the soil samples from
Airport residential farm were in the order
Zn[Pb[Cu[Ni[Cd[Cr whilst that of Dzorwulu
farm was in the order Zn[Pb[Cu[Ni[Cr[Cd.
The soils from the Airport farm were found to be contaminated
with Pb, Cu and Zn while the Dzorwulu farm
showed contamination for all the metals except Ni. All the
heavy metals were observed to have a high degree of
transfer from the soil into the lettuce except for Cr at the
Airport farm. Heavy metal concentrations in the lettuce
samples were all above the FAO/WHO recommended
levels. From the observations in this work, irrigation of
farm lands with untreated wastewater tends to introduce
contaminants into the soils which can be easily transferred
into the farm produce. The high levels of these heavy
metals pose a health risk to the consumers of such crops.